1. Field of the invention
This invention relates generally to trenching equipment and more particularly to holders for plow blades of the type used to rip a trench for the laying of cable, drainage pipe or other items.
2. Description of the Prior Art
The blades of prior art plows, trenchers, rippers and the like are generally connected behind a tractor at a fixed height, such that they may be forced along a path through the ground to generate a cut of fixed depth in the ground. Manual adjustment of the height of the blade is known. In U.S. Pat. No. 4,219,947 and corresponding Canadian patent no. 1,075,479, for example, a blade dog pivotally mounted on the blade holder is provided to lock the blade in the holder at selected heights by virtue of complementary recesses formed in the blade shank at various heights.
Manual adjustment in the prior art requires significant expenditures of time and effort in order to adjust the height of blade.
In some equipment, the height of the blade holder can be varied by moving the boom which supports the blade holder. However, this is an undesirable way of adjusting the height of the blade, since it is important for maximum pulling power and efficiency that the boom should be essentially horizontal.
There is thus a need for apparatus which would permit the height of the blade with respect to the blade holder, and thus the depth of the trench, to be varied readily by the operator, preferably from within the tractor cab.